Help deleting a mailbox folder

I have a problem that is giving me a headache. I tried importing mail from my external hard drive. It was about 99 messages. A new folder or mailbox was created with nothing in it. The name of the folder is 713.emlx. I have tried to delete the folder, but it won't go away. It asks me do I want to delete 713.emlx, 712.emlx, 710.emlx, etc. When I hit delete, the folder is still there. When I tried to move the folder it created another one that won't delete.

Please help.

Thanks.

bump.